Siemens 3VA1332-5GF42-0AF0 — 320 A SENTRON MCCB for Line Protection
The Siemens 3VA1332-5GF42-0AF0 is a 4-pole SENTRON molded case circuit breaker (MCCB) rated at 320 A continuous, designed for line protection in distribution panels. It carries a TM240 thermal-magnetic overcurrent release — the fixed thermal element and magnetic trip are calibrated for the 320 A frame, so the breaker protects cable and busbar runs rather than a specific motor load. The 187 kA interrupting rating at 240 V AC and 121 kA at 415 V AC give it the headroom for high-fault installations like transformer secondaries or large switchboards where available fault current exceeds 100 kA.
Breaking Capacity and Selectivity Planning
This MCCB's breaking capacity drops from 187 kA at 240 V to 75.6 kA at 500 V and 11.9 kA at 690 V. For a 400 V-class panel (common in European industrial distribution), the 121 kA at 415 V still covers most high-fault scenarios. The 4-pole design suits three-phase systems with a fully rated neutral — common in IT or TN-S earthing schemes where the neutral must be switched and protected. The rated insulation voltage of 800 V confirms the breaker can be applied on 690 V systems, though the interrupting rating at that voltage is the limiting factor.
Integration and Mounting
The breaker measures 248 mm high by 184 mm wide by 110 mm deep — a standard 4-pole MCCB footprint for a 320 A frame. It mounts directly to a panel backplate or into a Siemens SENTRON distribution board; no DIN-rail adapter is used at this current level. The TM240 release is non-interchangeable in the field — the thermal and magnetic settings are fixed at the factory for the 320 A rating. The auxiliary switch configuration (1 auxiliary + 1 trip alarm switch HQ) provides one N/O or N/C signal for status indication and a separate alarm contact that closes only on a trip event, which simplifies wiring to a PLC or remote annunciator.
Thermal Derating and Power Loss
At 40 °C ambient, the breaker carries its full 320 A. Derating begins at 55 °C (313 A) and reaches 292 A at 70 °C — the maximum operating temperature. The maximum power loss is 80.1 W at rated current, which matters for enclosure heat load calculations in a sealed panel. Storage temperature range is -40 °C to 80 °C, covering most warehouse and shipping conditions without special handling.